package functions.two;
interface Stream {
	int next();
}

class IntStream implements Stream {
	private int i = -1;
	public int next() {
		return ++i;
	}
}

interface Predicate{
	boolean evaluate(int j);
}

class FilteredStream implements Stream{
	private Stream it;
	private Predicate p;

	public FilteredStream(Stream it, Predicate p) {
		this.it = it;
		this.p =p;
	}

	public int next() {
		int i;
		do {
			i = it.next();
		} while (!p.evaluate(i));
		return i;
	}
}

class IsEven implements Predicate {
	public boolean evaluate(int j){
		return (j%2)== 0;
	}
}
class Main {
	public static void main (String[] args) {
		IntStream I = new IntStream();
		FilteredStream F = new FilteredStream(I, new IsEven());
		System.out.println(F.next());   // prints 0 on the screen
		System.out.println(F.next());   // prints 2 on the screen
		System.out.println(F.next());   // prints 4 on the screen
		System.out.println(F.next());   // prints 6 on the screen
		System.out.println(F.next());   // prints 8 on the screen

		IntStream J = new IntStream();
		J.next();                       // move forward one item in J
		FilteredStream G = new FilteredStream(J, new IsEven());
		System.out.println(G.next());   // prints 2 on the screen
		System.out.println(G.next());   // prints 4 on the screen
		System.out.println(G.next());   // prints 6 on the screen
		System.out.println(G.next());   // prints 8 on the screen

		IntStream K = new IntStream();
		class Div3 implements Predicate {
			public boolean evaluate(int n) { return (n%3) == 0; }
		}
		FilteredStream H = new FilteredStream(K, new Div3());
		System.out.println(H.next());   // prints 0 on the screen
		System.out.println(H.next());   // prints 3 on the screen
		System.out.println(H.next());   // prints 6 on the screen
		System.out.println(H.next());   // prints 9 on the screen
	}
}